P2X7 receptor modulation on microglial cells and reduction of brain infarct caused by middle cerebral artery occlusion in rat.

Abstract

Adenosine 5'-triphosphate outflow increases after an ischemic insult in the brain and may induce the expression of P2X7 receptors in resting microglia, determining its modification into an activated state. To assess the effects of P2X7 receptor blockade in preventing microglia activation and ameliorating brain damage and neurological impairment, we delivered the P2 unselective antagonist Reactive Blue 2 to rats after middle cerebral artery occlusion. In sham-operated animals, devoid of brain damage, double immunofluorescence verified the absence of P2X7 immunoreactivity on resting microglia, astrocytes, and neurons, identified, respectively, by OX-42, glial fibrillary acid protein, and neuronal nuclei (NeuN) immunoreactivity. After ischemia, vehicle-treated rats showed monolateral sensorimotor deficit and tissue damage in striatum and frontoparietal cortex. Moreover, P2X7 immunoreactivity was de novo expressed on activated microglia in infarcted and surrounding areas, as well as on a reactive form of microglia, resting in shape but P2X7 immunoreactive, present in ipsi- and contralateral cingulate and medial frontal cortex. Reactive Blue 2 improved sensorimotor deficit and restricted the volume of infarction, without preventing the expression of P2X7, but inducing it in the microglia of contralateral frontal and parietal cortex and striatum, which had lost reciprocal connections with the remote infarct area. De novo expression of P2X7 occurred in both activated and reactive microglia, suggesting their differentiated roles in the area of infarct and in remote regions. Reactive Blue 2 reduced ischemic brain damage, likely blocking the function of activated microglia in the infarct area, but in the remote brain regions promoted the expression of P2X7 on reactive microglia, developing defense and reparative processes.

• Authors: Alessia Melani, Susanna Amadio, Marco Gianfriddo, Maria G Vannucchi, Cinzia Volontè, Giorgio Bernardi, Felicita Pedata, Giuseppe Sancesario
• Journal: Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism (J Cereb Blood Flow Metab) Vol. 26 Issue 7 Pg. 974-82 (Jul 2006) ISSN: 0271-678X [Print] United States
• PMID: 16395292 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• P2rx7 protein, rat
• Purinergic P2 Receptor Antagonists
• Receptors, Purinergic P2
• Receptors, Purinergic P2X7
• Triazines
• Cibacron Blue F 3GA

Topics

• Animals
• Brain Ischemia (etiology, physiopathology, prevention & control)
• Cerebral Infarction (etiology, metabolism, prevention & control)
• Disease Models, Animal
• Dose-Response Relationship, Drug
• Infarction, Middle Cerebral Artery (complications, metabolism, physiopathology)
• Male
• Microglia (cytology, metabolism)
• Purinergic P2 Receptor Antagonists
• Rats
• Rats, Wistar
• Receptors, Purinergic P2 (biosynthesis, metabolism)
• Receptors, Purinergic P2X7
• Triazines (pharmacology)